Parametric Study of the Spring Force Line Effect on Vehicle Self Steer for MacPherson Strut Suspension System

The MacPherson strut is widely used in the automotive industry. Many investigations regarding the minimization of damper friction force have been published; however, this is not the case with vehicle self steer.

There are several methods to reduce the amount of vehicle self steer. The objective of this paper is to minimize vehicle self steer with respect to spring force line position. To investigate the relationship between vehicle self steer and spring force line, a mathematical model of suspension system was developed and then solved to obtain the optimum force line position that minimizes vehicle self steer.

The solution to the mathematical model found was that the force line must pass through the upper mount center in order to minimize vehicle self steer, or the force line must be on the same plane as the kingpin axis. Sensitivity analysis was performed to investigate the variability of the force line position on vehicle self steer. The result of the investigation will provide a guideline to design suspension coil spring with force line control.